Abstract Background Obesity is an established modifiable risk factor for multiple myeloma (MM). However, associations of obesity and MM risk in Black populations, for whom obesity and MM are more common, is less clear. Methods Using participants enrolled in the Integrative Molecular And Genetic Epidemiology study, we evaluated the association of anthropometric traits with MM risk overall, stratified by race and sex. Among cases, we assessed the association of BMI with the presence of myeloma-defining events. Results We observed an 18% increase in MM risk for every 5 kg/m 2 increase in usual adult BMI. Participants with severe obesity (BMI ≥ 40 kg/m 2 ) had the highest risk compared to those with a normal usual adult BMI (18.5–24.9 kg/m 2 ; OR = 1.87, 95% CI 1.25–2.80), particularly among Black men (OR = 3.94, 95% CI 0.90–17.36). Furthermore, MM cases with overweight/obesity (BMI ≥ 25 kg/m 2 ) were more likely to present at diagnosis with low renal function (OR = 1.62, 95% CI 1.09–2.40), deletion 13q (OR = 1.73, 95% CI 1.08–2.76) and lytic lesions or compression fractures (OR = 2.39, 95% CI 0.82–7.01) and less likely to present with severe diffuse osteopenia (OR = 0.51, 95% CI 0.31–0.81). Conclusions Findings underscore the importance of obesity as a modifiable risk factor for MM, particularly in high-risk populations, and for the clinical presentation of disease.
